Best place to buy really good quality lamps now is through
Lehman's Non-Electric Catalog. They won't sell anything low quality as they have a conscience. There are some things that they don't run in the catalog, but you can call them to order. One example of this is a tall Champion galvanized (not painted) lamp. These are also being made in China, but they are using the original dies and glass molds. Lehman's came through for me - I just put my name in, and the next time they got an order in (took a couple months), they hand-picked one for me! (I just checked: they DO have the tall Champion online.)
I'd been on the hunt for a Champion for years, because they have terrific light output (roughly 12 cp), and don't soot up easily. I gave up on finding an original (not common in my area of the country) and went for the reproduction.
For 'oil', I recommend using regular kerosene; in some of the really valuable old lamps, I use heating-grade kerosene as it contains no stains which will discolor the inside of a valuable old fount. You can find both at the big-box home improvement stores. For some of my old signal lamps which use a heavier fuel, I have been able to buy Jet A, which is essentially a heavier but clean, kerosene.
Fun Facts department: I'd been told by a couple old-timers that the Dietz Blizzard was their knockoff of the Champion, and the Jupiter was their knock-off of the Embury. However, neither has as much light output (due to the inability to infringe on patents) as the original.
I'm working on selling off most of my collection; it's time for 'the next guy' to own and enjoy them.